Metals, Molecules, and Star Formation in Sub-Damped Lyman-alpha Quasar Absorbers

Details Metals, Molecules, and Star Formation in Sub-Damped Lyman-alpha Quasar Absorbers Metals, Molecules, and Star Formation in Sub-Damped Lyman-alpha Quasar Absorbers

Aug 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009noao.prop..556k&link_type=abstract

NOAO Proposal ID #2009B-0556

Physics

Scientific paper

Damped Lyman-(alpha) (DLA) absorbers in quasar spectra have historically been used to probe neutral gas content of the universe, but show low metallicity at all redshifts, and evolve slower than model predictions. Surprisingly, our recent work showed that the sub- DLAs are more metal-rich and evolve faster than DLAs at 0.7 < z < 1.5. Furthermore, at these redshifts, the more metal-rich sub-DLAs usually show higher gas velocity dispersions. These findings, together with differences in [Mn/Fe] vs. metallicity trends, suggest different stellar populations for DLAs and sub-DLAs, possibly illustrating downsizing in galaxies. Here, we propose to test these ideas as follows: (1) We will double the metallicity samples at z < 0.7 and z > 1.5, and determine the metallicity evolution more accurately. (2) We will obtain much better estimates of trends in [Mn/Fe] and [Si/Fe] vs. metallicity in sub-DLAs , and whether they imply an early stellar population. (3) We will measure H_2 absorption lines in the high- z sub-DLAs, to understand how molecular content relates to metallicity and dust content. (4) We will constrain SFRs in high-z sub-DLAs by searching for C II* (lambda) 1336 absorption. Our data will provide fresh insights into the nature and relationship of DLA and sub-DLA populations, and their implications for galaxy evolution.

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